The invention is directed to formulating propylene-alpha-olefin polymer-based hot melt adhesive compositions.
Hot melt adhesive compositions are used in a variety of applications that require bonding two substrates together including, e.g., packaging applications (e.g., corrugated board and cardboard), nonwoven applications (e.g., disposable articles), bookbinding and footwear manufacturing. A hot melt adhesive composition is generally applied in a molten state and forms a bond as it cools and solidifies. The time required for a hot melt adhesive to cool to the point where it has enough strength to form a bond is referred to as the “set time.” Set time is an important parameter in applications that require high speed processing operations such as packaging and book binding operations. For many packaging applications, the bond needs to form rapidly or the resulting package will be poorly sealed or even unsealed.
It is important that adhesives used in packaging applications exhibit good bond strength over a wide temperature range and fast set times.
Amorphous polypropylene polymers have been formulated in hot melt adhesive compositions for a variety of applications. Many amorphous polypropylene polymers exhibit a long open time, are quite tacky immediately after solidifying from a molten state, and remain tacky for an undesirable period of time after solidifying. These properties are undesirable for applications that require short open times and nontacky properties after solidification.